Comparative study of toxic effects of zearalenone and its two major metabolites alpha-zearalenol and beta-zearalenol on cultured human Caco-2 cells.

Zearalenone (ZEN) is a fusarotoxin converted predominantly into alpha-zearalenol (alpha-Zol) and beta-zearalenol (beta-Zol) by hepatic hydroxysteroid dehydrogenases. The feeding of naturally contaminated grains with ZEN was associated with hyperestrogenic and adverse effects on humans and animals. There is a lack of information on the attribution of the toxic effects of these toxins. One wonders if these effects are due to the parent molecule (ZEN) or to its major metabolites (alpha-Zol and beta-Zol). Using human Caco-2 cells, we looked for the molecular mechanisms of toxicity of ZEN, alpha-Zol, and beta-Zol. Toxicity effects were studied by MTT viability assay and oxidative stress induction by measuring malondialdehyde (MDA) generation. To check whether the oxidative stress induction was associated to DNA lesions, we looked for DNA fragmentation by means of the Comet and the diphenylamine assays. To specify cell death pathway, we investigated caspase-3 activation, confirmed by poly(ADP-ribose) polymerase cleavage and by Bcl-2 depletion. Our results clearly demonstrated that ZEN as well as its two metabolites presented variable toxic effects. They induced cell death and an increase in MDA generation. These effects were associated to DNA fragmentation as well as caspase-3 activation. The observed toxic effects seem to be relieved by the metabolism of ZEN into alpha-Zol and beta-Zol.